wuzhengjie 2022-09-30 12:44:07 2022-09-30 12:44:28 16 返回题目
#include <bits/stdc++.h>
using namespace std;
int main(){
int n; cin>>n; double sum=0.0; for(int i=1;i<=n;i++){ if(i%2==1) sum+=1.0/i; else sum-=1.0/i; } cout<<fixed<<setprecision(3)<<sum; return 0;
}